Wet-etching devices are known with which disk-shaped objects, especially silicon wafers, are treated with a liquid etching medium to remove by etching a layer that is present on the disk-shaped object, e.g., an oxide layer on a silicon wafer.
Processes and devices are also known for etching wafers with an etching medium in gaseous form (dry etching). For example, an oxide layer of silicon wafers is removed by treating the wafer with hydrogen fluoride that is dissolved in nitrogen (HF vapors).
From DE 35 22 465 A it is known to protect a silicon wafer that is treated with a liquid etching medium on its underside by flushing it with deionized water before an etching attack. DE 35 22 465 A also mentions a ring gap, but this ring gap is determined by the geometric dimensions of a disk-shaped element and the wafer-side end of a supporting element. In the known device, the wafer is secured by separately applied negative pressure on the supporting element.